In U.S. Pat. No. 6,572,760 of the present inventor there is disclosed an anode for use in cathodic protection of steel members in concrete using sacrificial anodes to generate a current which acts to reduce corrosion of the steel or otherwise to effect restoration of the concrete.
The anode disclosed is formed of a mixture of zinc powder or particles which are pressed together with a quantity of a humectant which is also in powder form so as to create an anode body which is an intimately mixed structure. This provides a material in the anode itself which acts to enhance the current flow and also forms voids or pores where corrosion products can be absorbed. An alternative manufacture technique is also disclosed in which the powder is applied on one side of a sheet or between sheets of the zinc foil which is or are rolled to form the anode body.
The anode is shaped into a suitable body shape for use in concrete which can be a puck shaped body or strips or flat elements as required. These bodies form a particular exterior surface of a prescribed surface area which is in ionic contact with the medium. Some shapes have been designed which may increase the surface area in contact with the concrete, but even the most complex shapes have an increased contact ratio only of the order of 2, that is, the surface area is twice that of a more simply formed body.
The present applicant also has the following issued patents and pending applications in USA, the disclosures of which are incorporated herein by reference or may be referred to for further details of cathodic protection systems with which the present invention is concerned:
U.S. Pat. No. 6,793,800 issued Sep. 21, 2004.
U.S. Pat. No. 6,165,346 issued Dec. 26, 2000.
U.S. patent application Ser. No. 2004 0238376 published Dec. 2, 2004.
U.S. patent application Ser. No. 2005 0077191 published Apr. 14, 2005.
In International Publication WO98/16670 of Bennett and Clear which corresponds to U.S. Pat. No. 6,033,553 issued Mar. 7, 2000 is disclosed another cathodic protection system intended to be used as a surface arrangement. This arrangement relates to a thinly sprayed zinc or zinc alloy which is applied onto the surface of the concrete. This zinc or zinc coating is then used as an anode to supply current for the cathodic protection process. As the anode is exposed at the surface, this may be used either as a sacrificial system in which there is no applied current and the anode is gradually eroded as the electrolytic process proceeds or as an impressed current cathodic protection system. The improvement of the above Bennett application relates to the application of a humectant in free-flowing form which is positioned at the interface between the zinc anode coating and the concrete surface. It has been found and is disclosed in this application that the provision of the humectant in free-flowing form acts to absorb moisture from the area above the surface.